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Article

Research on the Properties of DOM from the Microalgal Treatment Process for Leachate from Incineration Fly Ash Based on EEM-PARAFAC Analysis

by
Yahan Yang
1,
Wenjing Pang
1,
Yuting Zheng
1,
Chuanhua Wang
1,
Qiongzhen Chen
1,
Qiang Ke
1,2,* and
Qi Wang
1,2,*
1
National and Local Joint Engineering Research Center of Ecological Treatment Technology for Urban Water Pollution, Department of Environmental Science, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China
2
Institute for Eco-Environmental Research of Sanyang Wetland, Wenzhou University, Wenzhou 325014, China
*
Authors to whom correspondence should be addressed.
Water 2024, 16(23), 3413; https://doi.org/10.3390/w16233413
Submission received: 21 October 2024 / Revised: 21 November 2024 / Accepted: 25 November 2024 / Published: 27 November 2024
(This article belongs to the Section Wastewater Treatment and Reuse)
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Abstract

:
Fly ash derived from the incineration of garbage is known to contain hazardous materials that can affect the growth of plants and animals and pose a threat to human health. In this study, we explored how treatment of fly ash leachate with microalgae could alter the properties of dissolved organic matter (DOM). Fly ash leachate samples obtained from a landfill site in Wenzhou were treated with the microalgae Chlorella vulgaris or Scenedesmus obliquus without and with the addition of ammonium ferric citrate (C6H8FeNO7) for 24 days, and changes in DOM levels and types were measured using excitation emission matrix fluorescence technology. The following results were obtained: Analysis of three-dimensional fluorescence spectral indices indicated that the algal treatment process consistently generated new autogenous DOM, with most of the organic matter being newly formed. Additional nutrients had a minor effect on the production and composition of DOM in the system. Using a parallel factor model to analyze the three-dimensional fluorescence spectral matrices of water samples from various systems revealed common components in each group, including arginine, tryptophan-like proteins and fulvic acid-like substances. This study aimed to explore the changes in DOM properties during microalgae treatment of fly ash leachate from the perspective of three-dimensional fluorescence.

1. Introduction

The continuous increase in the world population has led to the increasing production of garbage caused by human activities. Incineration is a widely used method in garbage treatment, both domestically and internationally, because it can efficiently reduce the volume and mass of the garbage. Incineration produces fly ash, which accounts for about 2–5% of the original waste volume and contains complex mixtures of pollutants, including toxic metals (e.g., lead, zinc, copper, chromium, cadmium, nickel) and organic compounds such as dioxins, VOCs, and PAHs [1,2,3,4,5]. Even after treatment, the fly ash still contains toxic metals, organic compounds and other substances, which may lead to serious pollution problems during its utilization [6]. There are already relevant studies exploring the potential application of MOF-COF hybrid materials in the degradation of organic pollutants [7]. Pan et al. [8] assessed the risk of fly ash from 15 urban waste incineration plants across the country. They found that over 40% of the samples had excessive leaching of Zn, Pb, and Cd, with Cd and Pb posing high environmental risks. Currently, the primary method for treating incinerated fly ash in China is solidification and stabilization before landfill disposal. During the sanitary landfill process, fly ash generates significant leachate as a result of factors like rainwater erosion, surface runoff, microbial decomposition, and groundwater infiltration. Landfill leachate often contains elevated emerging contaminant levels, posing a potential risk to localized groundwater [9].This leachate can enter the environment through membrane leakage, construction defects, or illegal discharge, threatening water bodies, soil, aquatic organisms, soil microorganisms, and the broader ecosystem, ultimately impacting human safety [10,11]. Sampling analysis near landfills has detected high levels of conventional pollutants such as ammonia nitrogen and COD, along with persistent organic pollutants including heavy metals, PAHs, PCBs, and emerging pollutants like pharmaceutical and personal care products (PPCPs) [12]. Thus, the safe treatment of leachate from fly ash landfills is an urgent issue that must be addressed.
Dissolved organic matter (DOM) is a complex mixture of humic substances, carbohydrates, proteins, and amino acids. In wastewater, DOM can adversely affect aquatic ecosystems by participating in the global carbon cycle and influencing the migration of other pollutants. Therefore, understanding the main components of DOM is crucial for targeted pollution reduction. Spectral methods are widely used to analyze the composition of DOM. Liu et al. utilized ultraviolet-visible absorption spectroscopy and three-dimensional excitation-emission matrix spectroscopy (3DEEMs) with parallel factor analysis (PARAFAC) to examine the DOM components in effluent from a membrane bioreactor (MBR), tap water, and surface water treated by the UF-RO process [13]. Their results showed that UF can remove 3.19–36.85% of aromatic DOM components and 5.71–32.25% of hydrophobic DOM components. All the water samples that these investigators examined predominantly contained protein-like and fulvic acid-like substances. Gan Shuchai et al. used fluorescence spectroscopy and PARAFAC to demonstrate that the oxidation of metals and sulfides in hypoxic sediments of the Rhone Delta affects their interaction with DOM, altering its fluorescence spectrum [14]. Jin Xincheng et al. combined PARAFAC with a self-organizing map to analyze the fluorescence spectrum of river DOM, indicating that the main source of humic substances in rivers is agricultural non-point pollution [15].
Researchers and environmentalists are exploring biomaterials as alternatives to synthetic adsorbents in various applications [16]. Compared with traditional physical or chemical treatment, biological treatment is characterized by being a simple process and low-cost [17]. Microalgae usually refer to microorganisms that contain chlorophyll a and are capable of photosynthesis. These algae are considered a type of protist [18]. There have been studies using microalgae to remove chemicals from wastewater [19,20]. Abou Shanab et al. used six different strains of microalgae to treat pig wastewater and found that some strains can remove total nitrogen and total phosphorus with high efficiency, yielding excellent results [21]. Combining microalgae cultivation with wastewater treatment avoids the need for chemical additives, and it can generate oxygen, reduce carbon dioxide emissions, and produce valuable biomass products [22]. Furthermore Muradov et al. were able to improve the treatment of pig wastewater by co-culturing various fungi with oil-producing microalgae [23]. Their results indicated enhancements in total biomass, lipid production rate, and wastewater bioremediation efficiency. Together, these studies show that fungi–microalgae particles can effectively remove pollutants. Large-scale algae and microalgae are renewable biological resources with great potential for sustainable development and environmental protection [24]. Several species of large algae and microalgae have been reported to accumulate large amounts of radioactive nuclides and corresponding concentration factors [25,26]. Algae can act as a biological adsorbent, making them suitable for removing various trace metal elements such as cadmium [27], but so far, mainly freshwater microalgae species have been studied [28]. At present, the application of algae in the ecological treatment of pollution is on the rise. For example, green algae are being considered a promising tool for detoxifying and removing pollutants (including drugs and their derivatives) from the environment [29]. Microalgae can reduce the turbidity, total suspended solids, total dissolved solids, nitrate and phosphate indices of wastewater [30]. Furthermore, the concentration of suspended solids in urban wastewater can be reduced through treatment with microalgae biofilm [31]. Andrea et al. studied the growth of Chlamydomonas sp. strain SW15aRL in various leachates, and the results showed that the SW15aRL strain could grow in a variety of leachates, and the ammonia nitrogen decreased by between 70% and 100% in the substrate where microalgae could grow successfully [32]. Haixing Chang et al. used chlorella in a membrane photobioreactor to recover nutrients from landfill leachate, and the results showed good microalgae lipid combustion performance [33]. Maroua El Ouaer et al. treated the leachate of a landfill in Tunisia with chlorella, and the results showed that when the leachate concentration was 10%, the ammonia nitrogen removal rate was as high as 90%, the maximum COD removal rate was 60%, and the lipid production efficiency was 4.74 mg·L−1d−1, indicating that microalgae are quite effective in the treatment of landfill leachate organic pollutants [34]. Catarina Viegas pretreated leachate with biomass ash chemical precipitation to reduce COD by 74% and color by 99%, and then inoculated six microalgae for bioremediation, including chlorella vulgaris and plagiophyllum spp. All achieved certain results, with removal efficiencies in the range of 18–62% for COD, 63–71% for N, and 15–100% for P [35].Although many studies have reported the application of microalgae in the treatment of landfill leachate, there are still few reports on the use of algae to treat fly ash landfill leachate.
Chlorella vulgaris and Scenedesmus obliquus are both single-celled freshwater microalgae. Both species can grow and reproduce rapidly in heterotrophic conditions as well as photoautotrophic conditions. Combining wastewater treatment with algae cultivation can reduce the cost of microalgae production, purify wastewater, and generate biomass energy. In this study, we examined the cultivation of microalgae in leachate taken from landfills, including fly ash. We specifically investigated the effects of initial leachate concentration and nutrient addition on the treatment efficiency. By analyzing changes in water quality indicators and using three-dimensional fluorescence spectroscopy combined with parallel factor analysis, the alterations in dissolved organic matter within the leachate treatment systems were evaluated. The findings could provide theoretical and technical support for the effective treatment of leachate at secure landfill sites.

2. Materials and Methods

2.1. Study Area

The leachate used in this study was taken from a safe landfill (121°4′12.828″ E, 27°59′49.502″ N) site in Wenzhou City, China. The site has a treatment capacity of 299,500 tons of garbage/year. Of this, 10,000 tons per year are disposed of by solidification treatment, 5000 tons by physical and chemical treatment, and 14,950 tons by incineration. Only the hazardous waste is incinerated, and this includes 4950 tons of medical waste. The storage capacity of the safe landfill site is 220,000 cubic meters.

2.2. Leachate Sampling

The leachate (pH: 7~9, COD: 1100 mg/L, NH3+-N: 3930 mg/L~4560 mg/L, turbidity: 21.2 NTU, SS: 47 mg/L) used in this study was taken from Wenzhou Comprehensive material Ecological disposal Center, which is located in the eastern highland of Xiaomen Island, Dongtou County, Wenzhou City. It is the first and only comprehensive disposal unit with incineration, physicochemical, solidification and landfill methods in Wenzhou, China.
Leachate samples were taken on 29 June 2020. The samples were taken at a depth of 0.5 m below the surface of the central sampling port. They were collected and transported back to the laboratory immediately, and parts of the samples were then subjected to three-dimensional fluorescence analysis to determine the types and concentration of DOM. The remaining parts of the samples were stored in a glass bottle and refrigerated in a refrigerator at 4 °C.

2.3. Selection and Treatment of Microalgae

2.3.1. Cultivation of Microalgae

Chlorella vulgaris (Fachb-8) and S. obliquus (FACHB-14) were purchased from the freshwater algae species bank of Chinese Academy of Sciences. They were cultured on BG11 medium in an illumination incubator at 25 °C, 20% illumination, and 12 h:12 h light–dark cycle. The algal cultures were shaken by hand three times a day to ensure that the algal cells were suspended evenly. BG11 medium for microalgal culture was purchased from the freshwater algal seed bank of Chinese Academy of Sciences.

2.3.2. Pretreatment of Microalgae

Chlorella vulgaris or S. obliquus culture (density of 106 cells/mL) was centrifuged at 3000× g for 5 min to harvest the algal cells. The cell pellet was resuspended in 0.18 mM NaHCO3 solution and then centrifuged as before. This step was repeated twice to remove any attached nutrients from the cells. After that, the cell pellet was resuspended in ultrapure water to an OD600 = ~1.1 and used in the subsequent treatment of leachate.

2.4. Experimental Setup

2.4.1. Dilution of Fly Ash Leachate

The original leachate sample contained high salinity, which could limit the growth of living organisms, and was not suitable for algae growth. In order to minimize such an effect, the leachate sample was added to the algal cultures to yield different final concentrations (1%, 10%, 20%, 25%, 30%, 40%, and 50%) of leachate (see Table 1). For the control, the culture contained BG11 medium instead of leachate. C. vulgaris and S. obliquus with OD680 = 1.1 ± 0.01 were inoculated into a conical flask containing the corresponding concentration of landfill leachate diluent with ultra-purified water at a concentration of 1 mL/10 mL, respectively. BG11 medium was used as control. All the experimental groups were placed in the light incubator, the culture temperature was 25 °C, the illumination was 20%, and the light–dark cycle ratio was 12 h:12 h. The algal cells were suspended evenly by shaking the liquid three times a day, and samples were taken from each culture for analysis of fluorescence indexes: Fn (280) and Fn (355). The measurement was taken once every 4 days.

2.4.2. Nutrients

As the pollutants in the leachate are complex and there are nutrients for algae growth, but also some nutrient deficiencies, additional nutrients should be added to the leachate to explore the removal efficiency of leachate pollutants by algae under the condition of adding nutrients. In addition, K2HPO4·3H2O, MgSO4·7H2O, ammonium ferric citrate and trace elements were selected for the preparation of BG11 medium. The specific experimental group settings are shown in Table 2.
Chlorella vulgaris and S. obliquus were inoculated with 1 mL/10 mL of OD680 = 1.1 ± 0.01 in each solution. The culture conditions and sampling frequency were consistent with the experiment.

2.5. Determination of DOM in Leachate

The experiment was conducted at 25 degrees Celsius. The leachate samples were first filtered through a 0.45 μm filter membrane before they were analyzed by three-dimensional fluorescence spectroscopy. The experiment used a fluorescence spectrometer (Hitachi F-4600, Japan) with a xenon lamp as the excitation light source. The excitation wavelength scanning range was set at 200–500 nm, the slit bandwidth at 5 nm, the emission wavelength scanning range at 250–600 nm, the slit bandwidth at 2 nm, and the scanning speed at 1200 nm/min. The experiment was conducted in a 1 cm quartz fluorescence colorimetric dish, using Milli-Q ultrapure water (Milli-Q® IQ 7000, Germany) as blank control. The EEM of the sample was subtracted from that of the blank control to correct for the fluorescence region affected by Rayleigh scattering and Raman scattering.

2.6. Parallel Factor Analysis

The parallel factor analysis algorithm (PARAFAC) is an algorithm based on the principle of alternating least squares to achieve matrix factorization of multidimensional data. After breaking down the three-dimensional whole column composed of multiple EEM data into three load matrices, the three-dimensional fluorescence spectrum of the DOM in the three load matrices was analyzed. The data were processed with Excel, and then subjected to corresponding parallel factor analysis in MATLAB R2018b software.

3. Results

3.1. Fluorescence Characteristic Parameter

The fluorescence index (FI) refers to the ratio of fluorescence intensity between Ex at 370 nm and Em at 450 nm and 500 nm, and it represents the proportion of microbial derived organic matter to total organic matter. When FI > 1.9, the main sources of DOM comes from microbial and algal activities (endogenous), with obvious characteristics of autotrophic sources; when FI < 1.4, the endogenous contribution is relatively low, mainly due to external inputs.
The biological index (BIX) refers to the ratio of fluorescence intensity of Em at 380 nm and 430 nm when Ex is at 310 nm. It mainly reflects the relative contribution of endogenous sources and is also used to evaluate their bioavailability. When BIX is between 0.6 and 0.8, it indicates that the contribution of autogenic sources is relatively small; when BIX is between 0.8 and 1.0, it indicates the presence of a significant amount of newly generated autogenous DOM; when BIX > 1.0, it indicates that DOM is mainly derived from autogenous sources and the organic matter is newly generated.
When Fn (355) is determined at Ex = 355 nm, the maximum fluorescence intensity of Em between 440 and 470 nm can characterize the relative concentration level of humic substances. Thus, when Fn (280) is obtained at Ex of 280 nm, the maximum fluorescence intensity of Em between 340 and 360 nm can reflect the relative concentration level of protein-like substances.

3.2. Influence of Leachate Dilution Concentration on Fluorescence Index

Differences in initial leachate concentrations led to significant differences in the initial values of Fn (280) among different groups, meaning that there was a significant difference in the content of proteins among groups (Figure 1a–c), and the range of changes in Fn (280) with lower initial leachate concentration was larger. The values of Fn (280) in the C. vulgaris cultures showed an increasing trend under various leachate concentrations, while the S. obliquus cultures showed an increasing trend except when BG11 medium and 1% leachate were used. At other leachate concentrations, the initial values were already high and fluctuated around the initial values. A slight increasing trend in Fn (280) was also observed at 1% and 10% leachate concentrations, while the increasing trends shown by other leachate concentrations were not significant. All groups fluctuated within a certain range. The results indicated that the photosynthetic and growth processes of C. vulgaris that occurred during the treatment of leachate produced proteins. However, the proteins may also be due to the high protein content released by C. vulgaris into the system caused by the rupture and decomposition of algal cells in the later stage of growth.
The different dilution concentrations of leachate also resulted in significant differences in the content of humic substances in each group, as shown by the significant differences in Fn (355) among the groups (Figure 1d–f). Compared with protein-like substances, the concentration of humic substances in the system changed very little, especially for the S. obliquus plus leachate system, with only a very small and stable increase. Consistent with the changes due to protein-like substances, the concentration of humic substances in the C. vulgaris-treated systems also showed significant changes. Except for a significant decrease when the leachate dilution concentrations were 30%, 40%, and 50%, there was an overall increasing trend, indicating that the humic substances in the system increased with the growth and decay of a large number of algal cells.
Under different dilution concentrations of leachate, the growth activity of the algae varied, with high concentrations exerting a certain inhibitory effect on the growth activity of the algae. The FI values of C. vulgaris and S. obliquus in the presence of fly ash leachate were higher than in its absence (cultures containing BG11 medium instead of leachate). When the leachate concentration was 1%, the FI value was relatively low, and in the case of C. vulgaris, a large FI fluctuation range was detected, and this could be related to the lower leachate concentration, consequently leading to fluctuation in nutrient levels in the system. Chlorella vulgaris yielded an FI value when the culture contained 10% leachate, but the FI value appeared to decrease with increasing leachate concentrations. This could mean that as the fly ash leachate concentration increased, the extracellular release of algae and bacteria and the intensity of exudate activity weaken (Figure 2a,b).
A biological source index (BIX) of greater than 0.8 was obtained regardless of the concentration of fly ash leachate in the algal cultures. This could indicate the presence of a large amount of self-generated DOM that appeared during the treatment process, and the organic matter was mostly newly generated. At the same time, the BIX value showed a downward trend in response to increasing leachate concentrations, accompanied by a corresponding weakening in algal growth activity, consistent with the growth of high-concentration alga decreases, and correspondingly, the activity of algae was relatively weak (Figure 2c,d).

3.3. The Impact of Additional Nutrients

Consistent with the results of the three-dimensional fluorescence spectrum, the fluorescence of humic and protein-like substances in the cultures of groups A4, A6, A7, and A8 was masked during the first measurement probably because of the addition of ammonium ferric citrate, resulting in significantly lower values of Fn (280) (Figure 3a,b) and Fn (355) (Figure 3c,d) compared to the cultures from the other groups. The C. vulgaris groups produced a higher Fn (280) than the S. obliquus groups, meaning that these cultures contained higher protein content. This is consistent with the previous explanation that C. vulgaris itself contains a higher level of cellular protein. Both C. vulgaris and S. obliquus produced very similar levels of humus-like substances, since no significant difference in the migration and transformation of humus-like substances between the two algae was detected during the treatment of leachate. The main difference was seen in protein substances.
In the presence of added nutrients, both C. vulgaris and S. obliquus cultures with fly ash leachate displayed an FI > 1.9 (Figure 3e,f) and a BIX > 1.0 (Figure 3g,h). At the same time, there was no significant difference in FI and BIX values among the different conditions, especially in the case of BIX, in which differences in values were very small. This indicates that organic matter in the system is mainly derived from the extracellular release of bacteria and algae, as well as microbial activities such as exudate. DOM is mainly derived from autotrophic sources, and organic matter is newly generated.

3.4. PARAFAC

3.4.1. Influence of Leachate Concentration

The different concentrations of fly ash leachate affected the concentration of various substances, but the types of substances remained the same. Different initial concentrations of leachate yielded similar peak positions and fluorescent intensities for the two fluorescent components of the two algal culture systems. Component 1 had obvious excitation wavelengths at 255 nm and 345 nm, with the maximum emission wavelength at around 420 nm, reflecting the fluorescence peaks formed by the two types of fulvic acids. Component 2, on the other hand, had a significant excitation wavelength at 275 nm, with a maximum emission detected at around 370 nm, reflecting the fluorescence peak formed by soluble microbial products (Figure 4a,b).

3.4.2. Impact of Additional Nutrients

Adding additional nutrients changed the material composition of the system, and this was reflected in the changes in the fluorescence components of the cultures. Three fluorescent components were obtained from the water samples of C. vulgaris before and after the addition of nutrients (Figure 5a). Component 1 had obvious excitation wavelengths at 240 nm and 290 nm, with a maximum emission wavelength around 390 nm, reflecting the fluorescence peaks formed by the two types of humus. Component 2 exhibited significant excitation at 260 nm and 340 nm, with a maximum emission wavelength at around 420 nm, reflecting the fluorescence peaks formed by the two types of fulvic acids. Component 3 exhibited significant excitation at 240 nm and 275 nm, with a maximum emission at around 310 ± 10 nm, reflecting the fluorescence peaks formed by complex amino acids and soluble microbial products. The peak corresponding to the emission at 560 nm following excitation at 275 nm could reflect the fluorescence peak formed by fulvic acid substances.
Before and after the addition of nutrients, two fluorescent components were obtained from the water samples of C. vulgaris (Figure 5b) culture, which were basically consistent with the substances characterized by Component 1 and Component 2. The fluorescence intensity of Component 2 was similar, while Component 1 reflected different fluorescence intensities corresponding to the two types of humus. Component 1 of C. vulgaris represented two types of humus fluorescence intensities of 0.32 and 0.28, while Component 1 of C. vulgaris represented two types of humus fluorescence intensities of 0.28 and 0.33, respectively. This indicated that there were differences in the migration and transformation of substances among different algal species during the treatment process.

4. Conclusions

Overall, the findings of this study indicated that whether by changing the dilution concentration of the leachate or adding nutrients, the experimental group with added C. vulgaris produced more proteins during the treatment process compared to the experimental group with added S. obliquus. However, the content of humic-like substance in the two microalgae groups did not change much. Around the 12th day of the experiment in the C. vulgaris group and around the 10th day in the S. obliquus experimental group, there was a significant decrease in the content of humic-like substance and proteins in each experimental group, indicating that microalgae had the highest treatment efficiency at this time. When adding additional nutrients to the leachate experimental group, the overall content of proteins and humic-like substances in each group showed a downward trend. When the dilution concentration of the leachate was 10%, the FI values and activity of the C. vulgaris group were the highest. When the dilution concentration of the leachate was 25%, the FI values and activity of the S. obliquus group were the highest. The BIX values of C. vulgaris and S. obliquus. decreased with the increase in leachate dilution concentration, indicating that the bioavailability of the solution decreased with the increase in leachate dilution concentration. The change in leachate concentration affected the concentration of DOM produced during the process, but did not affect the type of DOM. Adding additional nutrients will change the DOM composition of the system. The effect of additional nutrients only had a relatively small impact on the production and composition of DOM in the system, but the addition of ammonium ferric citrate, a photochemically sensitive substance, may interfere with the measurement of three-dimensional fluorescence spectra. The specific mechanism of action and the timeliness of interference need further study and confirmation.

Author Contributions

Conceptualization, Q.W. and C.W.; methodology, Y.Y., W.P., Q.W. and Q.K.; software, Y.Y. and W.P.; investigation, W.P., Q.K. and Q.C.; data curation, Y.Y., Q.W., Y.Z. and W.P.; writing—original draft preparation, Y.Y., W.P. and Q.W.; writing—review and editing, Y.Y., Q.W. and W.P.; supervision, Q.W., C.W. and Q.K.; funding acquisition, Q.W. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Science and Technology Major Program of Wenzhou, China (Grant No.ZS2022005), Zhejiang Provincial Department of Education research project, China (Grant No. Y202352832), and the Research Project of Wenzhou Ecological Park Management Committee (SY2022ZD-1001-01).

Data Availability Statement

Data are contained within the article.

Acknowledgments

We thank Alan K Chang (Wenzhou University) for his useful discussions and kind efforts in revising the language of this manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

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Water 16 03413 g001aWater 16 03413 g001b
Figure 1. Effect of leachate concentration on fluorescence intensity of the algal cultures. (a–c) Fn (280); (d–f) Fn (355).
Figure 1. Effect of leachate concentration on fluorescence intensity of the algal cultures. (a–c) Fn (280); (d–f) Fn (355).
Water 16 03413 g001aWater 16 03413 g001b
Water 16 03413 g002aWater 16 03413 g002b
Figure 2. Changes in fluorescence index under different dilution concentrations of leachate. (a,b) FI; (c,d) BIX.
Figure 2. Changes in fluorescence index under different dilution concentrations of leachate. (a,b) FI; (c,d) BIX.
Water 16 03413 g002aWater 16 03413 g002b
Water 16 03413 g003aWater 16 03413 g003b
Figure 3. Changes in various indicators under conditions of added nutrients. (a,b) Fn (280); (c,d) Fn (355); (e,f) Fluorescence index FI; (g,h) Biosource Index (BIX).
Figure 3. Changes in various indicators under conditions of added nutrients. (a,b) Fn (280); (c,d) Fn (355); (e,f) Fluorescence index FI; (g,h) Biosource Index (BIX).
Water 16 03413 g003aWater 16 03413 g003b
Water 16 03413 g004
Figure 4. EEMs and maximum excitation/emission wavelength distribution of DOM components in water samples from different algal systems. (a) C. vulgaris system; (b) S. obliquus system.
Figure 4. EEMs and maximum excitation/emission wavelength distribution of DOM components in water samples from different algal systems. (a) C. vulgaris system; (b) S. obliquus system.
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Water 16 03413 g005
Figure 5. EEMs and maximum excitation/emission wavelength distribution of DOM components in water samples of two types of algae before and after treatment with added nutrients. (a) C. vulgaris; (b) S. obliquus.
Figure 5. EEMs and maximum excitation/emission wavelength distribution of DOM components in water samples of two types of algae before and after treatment with added nutrients. (a) C. vulgaris; (b) S. obliquus.
Water 16 03413 g005
Table 1. Setting of the experimental group of leachate dilution concentration.
Table 1. Setting of the experimental group of leachate dilution concentration.
Base FluidBG111%
Leachate		10%
Leachate		20%
Leachate		25%
Leachate		30%
Leachate		40%
Leachate		50%
Leachate
C. vulgarisA0A1A2A3A4A5A6A7
S. obliquusB0B1B2B3B4B5B6B7
Without algae/C1C2C3C4C5C6C7
Table 2. The setting of the nutrient experiment group.
Table 2. The setting of the nutrient experiment group.
C. vulgarisS. obliquusK2HPO4·3H2O (g/L)MgSO4·7H2O (g/L)C6H11FeNO7 (g/L)Trace Elements (mL/L)
A1B10.2000.07500
A2B20001
A3B30.2000.07501
A4B40.20000.0601
A5B50000
A6B600.0750.0601
A7B70.20000.0600
A8B800.0750.0600
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Yang, Y.; Pang, W.; Zheng, Y.; Wang, C.; Chen, Q.; Ke, Q.; Wang, Q. Research on the Properties of DOM from the Microalgal Treatment Process for Leachate from Incineration Fly Ash Based on EEM-PARAFAC Analysis. Water 2024, 16, 3413. https://doi.org/10.3390/w16233413

AMA Style

Yang Y, Pang W, Zheng Y, Wang C, Chen Q, Ke Q, Wang Q. Research on the Properties of DOM from the Microalgal Treatment Process for Leachate from Incineration Fly Ash Based on EEM-PARAFAC Analysis. Water. 2024; 16(23):3413. https://doi.org/10.3390/w16233413

Chicago/Turabian Style

Yang, Yahan, Wenjing Pang, Yuting Zheng, Chuanhua Wang, Qiongzhen Chen, Qiang Ke, and Qi Wang. 2024. "Research on the Properties of DOM from the Microalgal Treatment Process for Leachate from Incineration Fly Ash Based on EEM-PARAFAC Analysis" Water 16, no. 23: 3413. https://doi.org/10.3390/w16233413

APA Style

Yang, Y., Pang, W., Zheng, Y., Wang, C., Chen, Q., Ke, Q., & Wang, Q. (2024). Research on the Properties of DOM from the Microalgal Treatment Process for Leachate from Incineration Fly Ash Based on EEM-PARAFAC Analysis. Water, 16(23), 3413. https://doi.org/10.3390/w16233413

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